The complete or partial detachment of ligaments, tendons, and/or other soft tissues from their associated bones within the body are relatively commonplace injuries, particularly among athletes. Such injuries are generally the result of excessive stresses being placed on these tissues. By way of example, tissue detachment may occur as the result of an accident such as a fall, over-exertion during a work-related activity, during the course of an athletic event, or in any one of many other situations and/or activities.
In the case of a partial detachment, the injury will frequently heal itself, if given sufficient time and if care is taken not to expose the injury to further undue stress. In the case of complete detachment, however, surgery may be needed to re-attach the soft tissue to its associated bone or bones. Numerous devices are currently available to re-attach soft tissue to bone. Examples of such currently-available devices include screws, staples, suture anchors, and tacks. In soft tissue re-attachment procedures utilizing screws, the detached soft tissue is typically moved back into its original position over the bone. The screw is then screwed through the soft tissue and into the bone, with the shank and head of the screw holding the soft tissue to the bone. Similarly, in soft tissue re-attachment procedures utilizing staples, the detached soft tissue is typically moved back into its original position over the bone. The staple is then driven through the soft tissue and into the bone, with the legs and bridge of the staple holding the soft tissue to the bone.
In soft tissue re-attachment procedures utilizing suture anchors, an anchor-receiving hole is generally first drilled in the bone at the desired point of tissue re-attachment. A suture anchor is then deployed in the hole using an appropriate installation tool. This effectively locks the suture to the bone, with the free end(s) of the suture extending out of the bone. The free end(s) of the suture are passed through or around the soft tissue and are used to tie the soft tissue securely to the bone.
While current suture anchors are effective in anchoring soft tissue to bone, one drawback with current devices is that the suture and soft tissue attached thereto can slip or otherwise move while the suture anchor is being driven into the bone. Once the suture anchor has been driven into bone, the suture and the soft tissue cannot be adjusted to adjust the position of the soft tissue relative to the bone because the driven suture anchor holds the suture and soft tissue in place. The soft tissue may therefore not be in an optimal position to facilitate healing. Even if the suture and the soft tissue can be adjusted after the suture anchor has been driven into bone, tying the suture into a knot can cause the soft tissue to slip from an optimal position.
Another drawback with current devices is that the suture anchor must have a head with a length that is sufficient to withstand a torque applied thereto by a driver. As a result of the increased length, the suture anchor will typically extend at least partially into underlying soft cancellous bone in order to position the head beneath the outer surface of the bone. The bone-engaging portion of the suture anchor will thus be mostly disposed within and engaged with cancellous bone, rather than cortical bone. This is due to the fact that the cortical bone is only about 1 mm to 3 mm in length, and the driver head is often longer than 3 mm. Once implanted, tension applied to the anchor via the sutures can cause the anchor to migrate into the cortical bone and thus the head of the suture anchor can become proud, resulting in a weak fixation among other problems.
Accordingly, there remains a need for improved methods and devices for attaching soft tissue to bone.